Dear Editor

We thank Dr Perera [1] for his interest in our article.[2] We do agree with him that the results of partial flaps without ablation and good flaps with ablation are not comparable, which in fact was not the aim of the study.

The primary aim of the study was to evaluate the changes in the posterior corneal elevation after the partial flaps. We, in this article, attempted to evaluate the changes in posterior corneal elevation after partial flaps in cases that were planned to have LASIK surgery. Based on our results we concluded that the inadvertent occurrence of partial flap during LASIK procedure does not contribute to an additional increase in posterior corneal elevation. Further, we only suggested, but did not conclude that evaluation of the posterior corneal surface topographic changes after partial flaps without ablation may help us to understand the contribution of the flap (even if it is partial) to the corneal elasticity. This is more so as raising a flap alone in the absence of photo ablation for the purpose of studying the mechanism of posterior corneal elevation may be not be practical and ethical.

References

(1) Perera S. Partial flaps during LASIK [electronic response to Sharma et al. Posterior corneal topographic changes after partial flap during laser in situ keratomileusis] bjophthalmol.com 2003 http://bjo.bmjjournals.com/cgi/eletters/87/2/160#121

(2) N Sharma, A Rani, R Balasubramanya, R B Vajpayee, and R M PandeyPosterior corneal topographic changes after partial flap during laser in situ keratomileusis. Br J Ophthalmol 2003;87:160-162.

Dear Editor

I read this article with interest.[1] Here, the authors suggest that the evaluation of the posterior corneal surface topographic changes after partial flaps without ablation may help us to know the contribution of the flap to the corneal elasticity and the increase in posterior corneal elevation following LASIK. However, I would like to point out that there are some very important differences between a failed flap and a ablatable flap. Firstly, as in their own study, some patients with partial flaps had the hinge in the visual axis. This means that in these patients the flaps have cut half or less of the central corneal bed, compared to a good flap which cuts through the whole of the central area. Secondly the so called thin flaps that were not ablated are most likely to be epithelial or subepithelial flaps with very little stromal tissue. Due to these facts any conclusions drawn from partial flaps without ablation, on the possible outcomes of good flaps with ablation are invalid and erroneous.

References

(1) N Sharma, A Rani, R Balasubramanya, R B Vajpayee, and R M Pandey. Posterior corneal topographic changes after partial flap during laser in situ keratomileusis. Br J Ophthalmol 2003;87:160-162.